The present invention relates to modification of the lens member component for a sealed beam lamp unit having an inner surface of the lens member component with prism elements to focus light transmitted therethrough and further having an outer sealing rim with front and back sealing surfaces joined by a body section. Said pressed glass sealed beam lamp unit has particular utility for automotive headlights. Circular-shaped headlights having such lens member construction have been used in motor vehicles for some time and can be hermetically sealed without undue difficulty except when the sealing rim of the lens member is warped. This defect is attributable to uneven thermal contraction of the lens members in the mold during initial formation. The front sealing surface of a warped lens member is not flat so as to lie in the same spatial plane and is believed to result from thickness variation of the prism elements on the inner surface of the lens member. Said defect is more frequently encountered on heavily fluted lens members which include rib elements longitudinally extending along the inner surface that tend to cool earlier than the rest of the inner surface. When a circular-shaped pressed glass lens member having a warped sealing rim is thereafter hermetically sealed to the rim of a correspondingly shaped reflector member, it becomes possible to damage the aluminum surface with the gas flames customarily employed to effect hermetic sealing. The gap existing between said sealing surfaces can also produce an unreliable fusion seal.
The more recently introduced rectangular-shaped headlight unit has proven more difficult to fusion seal the individual components together by reason of further deformities produced by uneven thermal contraction when said individual lens and reflector members are initially pressed in glass molds. Thermal contraction of the reflector member customarily produces a convex contour for the front sealing surface of the sealing rim whereas the correspondingly shaped pressed glass lens member usually experiences a mismatching deformation attributable to the rectangular shape of said lens member as well as thickness variation of the prism elements disposed on the inner surface. These mismatching deformities interfere with proper registration of the individual members for hermetic sealing since the deformities can be sufficiently prominent to produce actual bowing of the front sealing surfaces in the rim regions of both glass members. The sealing problem becomes especially severe if such bowing results in a convex deformity in one member while the remaining member has a concave deformity not coincident with the bowing in the other member.